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net: make V2Transport send uniformly random number garbage bytes

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This commit is contained in:
Pieter Wuille
2023-07-30 11:43:10 -04:00
parent 0be752d9f8
commit 3ffa5fb49e
3 changed files with 46 additions and 14 deletions
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27
src/net.cpp
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@@ -987,20 +987,26 @@ V2Transport::V2Transport(NodeId nodeid, bool initiating, int type_in, int versio
m_recv_state{initiating ? RecvState::KEY : RecvState::KEY_MAYBE_V1},
m_send_state{initiating ? SendState::AWAITING_KEY : SendState::MAYBE_V1}
{
// Initialize the send buffer with ellswift pubkey.
m_send_buffer.resize(EllSwiftPubKey::size());
// Construct garbage (including its length) using a FastRandomContext.
FastRandomContext rng;
size_t garbage_len = rng.randrange(MAX_GARBAGE_LEN + 1);
// Initialize the send buffer with ellswift pubkey + garbage.
m_send_buffer.resize(EllSwiftPubKey::size() + garbage_len);
std::copy(std::begin(m_cipher.GetOurPubKey()), std::end(m_cipher.GetOurPubKey()), MakeWritableByteSpan(m_send_buffer).begin());
rng.fillrand(MakeWritableByteSpan(m_send_buffer).subspan(EllSwiftPubKey::size()));
}
V2Transport::V2Transport(NodeId nodeid, bool initiating, int type_in, int version_in, const CKey& key, Span<const std::byte> ent32) noexcept :
V2Transport::V2Transport(NodeId nodeid, bool initiating, int type_in, int version_in, const CKey& key, Span<const std::byte> ent32, Span<const uint8_t> garbage) noexcept :
m_cipher{key, ent32}, m_initiating{initiating}, m_nodeid{nodeid},
m_v1_fallback{nodeid, type_in, version_in}, m_recv_type{type_in}, m_recv_version{version_in},
m_recv_state{initiating ? RecvState::KEY : RecvState::KEY_MAYBE_V1},
m_send_state{initiating ? SendState::AWAITING_KEY : SendState::MAYBE_V1}
{
// Initialize the send buffer with ellswift pubkey.
m_send_buffer.resize(EllSwiftPubKey::size());
assert(garbage.size() <= MAX_GARBAGE_LEN);
// Initialize the send buffer with ellswift pubkey + provided garbage.
m_send_buffer.resize(EllSwiftPubKey::size() + garbage.size());
std::copy(std::begin(m_cipher.GetOurPubKey()), std::end(m_cipher.GetOurPubKey()), MakeWritableByteSpan(m_send_buffer).begin());
std::copy(garbage.begin(), garbage.end(), m_send_buffer.begin() + EllSwiftPubKey::size());
}
void V2Transport::SetReceiveState(RecvState recv_state) noexcept
@@ -1126,16 +1132,18 @@ void V2Transport::ProcessReceivedKeyBytes() noexcept
SetSendState(SendState::READY);
// Append the garbage terminator to the send buffer.
size_t garbage_len = m_send_buffer.size() - EllSwiftPubKey::size();
m_send_buffer.resize(m_send_buffer.size() + BIP324Cipher::GARBAGE_TERMINATOR_LEN);
std::copy(m_cipher.GetSendGarbageTerminator().begin(),
m_cipher.GetSendGarbageTerminator().end(),
MakeWritableByteSpan(m_send_buffer).last(BIP324Cipher::GARBAGE_TERMINATOR_LEN).begin());
// Construct garbage authentication packet in the send buffer.
// Construct garbage authentication packet in the send buffer (using the garbage data which
// is still there).
m_send_buffer.resize(m_send_buffer.size() + BIP324Cipher::EXPANSION);
m_cipher.Encrypt(
/*contents=*/{},
/*aad=*/{}, /* empty garbage for now */
/*aad=*/MakeByteSpan(m_send_buffer).subspan(EllSwiftPubKey::size(), garbage_len),
/*ignore=*/false,
/*output=*/MakeWritableByteSpan(m_send_buffer).last(BIP324Cipher::EXPANSION));
@@ -1490,7 +1498,10 @@ void V2Transport::MarkBytesSent(size_t bytes_sent) noexcept
m_send_pos += bytes_sent;
Assume(m_send_pos <= m_send_buffer.size());
if (m_send_pos == m_send_buffer.size()) {
// Only wipe the buffer when everything is sent in the READY state. In the AWAITING_KEY state
// we still need the garbage that's in the send buffer to construct the garbage authentication
// packet.
if (m_send_state == SendState::READY && m_send_pos == m_send_buffer.size()) {
m_send_pos = 0;
m_send_buffer = {};
}